a handbook of the mosquitoes of north america - Systematic Catalog ...

110 MOSQUITOES OF NORTH AMERICA
brood from late May till the middle of October provided there
is sufficient rain to keep the pools filled. Dyar believes this
species. was originally single brooded, breeding during the early
spring in pools filled by the melting snows and spring rains
but that now the species breeds whenever water fills the pools
in which their eggs have been laid. Freeborn states that “Gn-
like the eggs of many Aedes, those of vexans hatch if moisture
is supplied during the same season. This facilitates, in favored
locations, the production of many broods during the season.”
He finds, in California, that along rivers that overflow their
banks whenever there is excessive rainfall in the mountains or
melting snows, a new brood of v-dcxam appears in the lo8w-
lying depressions filled by the water. In other sections, as the
Sacramento Valley, there is only a single brood, the spring
brood, since there are no summer rains.
Our observations indicate two distinct breeding periods in
Central New York. The spring brood develops in May if
there is sufficient rainfall but if not, it develops in June or
July should rains occur then. The second breeding period oc-
curs in late August and early September and this brood rarely
fails since sufficient rainfall generally occurs at that time.
Migration of the Adults. The adults migrate considerable
distances from their breeding grounds. Smith states that they
travel a mile or two with ease and a five mile migration is
possible. Beckwith concludes that the species has an extreme
migratory range of ten miles and tends to move to the nearest
center of population. At Ithaca I found the species to migrate
rather slowly and gradually. The disappearance of the adults
at the breeding grounds was indicated by their presence in the
city about one-half mile distant. It took about a week to cover
a three mile radius to the outlying districts. The adults later
return to their breeding grounds and the females deposit their
eggs on the dry hard ground. They have not been seen to ovi-
posit on water or where water was present. Aedes vexam
bites readily and is a very annoying pest in rural districts,
villages, cities and suburban areas. Its maximum abundance